Development Of New Type Of DFB Laser Frequency Stabilization System And Phase Invariance DDS

The laser frequency stabilization system is made an important improvement by using a combination of Zeeman effect and the saturation absorption technology DFB laser frequency stabilization method,the background of which is the research of laser cooling cesium atomic clock.As the microwave leakage can cause frequency shifts, a method of using DDS technology to suppress frequency shift introduced by the leakage of microwave of the atomic fountain clock is developed.The cesium atomic will become a real keep time device if it has a second pulse generator. The second pulse generator based on the FPGA technology is developed.This article includes three parts:The first part:DFB laser frequency stabilization based on Zeeman effect and saturated absorptionThis part introduces a method of using Zeeman effect and saturated absorption technique to extract the frequency error from a Cs vapor cell and use digital PID control technology to feedback control the DFB laser current (slow-loop control), and use analog PI to control the FET current control port(fast-loop control) to achieving the DFB laser frequency stabilization and make the line width narrowed. This method has both the advantages of Zeeman effect technique and the saturated absorption technique, with high spectral resolution and modulation-free. For its high speed and flexibility, a C8051F micro-controller is introduced to realize the digital PID, so the system is more reliable in performance and easier to be realized. When the laser frequency is locked to Cs D2 lines F=4â†'F`=4,5 crossover transition, the frequency of peak-peak(p-p) ups and downs is about 1.6MHz and relative frequency fluctuation is better than 4.5×10-7, which meets the requirements of a small fountain clock. The Second part:Design DDS for microwave leakage frequency shift suppressionThis part introduces a method of using DDS technology to suppress frequency shift introduced by the leakage of microwave in the atomic fountain clock. The principle of microwave leakage frequency shift suppression and the DDS circuit realization based on the FPGA are mainly introduced. This paper also gives the simulation of the FPGA design. From the experiment result of fountain clock the introduced frequency shift by switch DDS output frequency should be less than 2×10-16.The Third part:Design second pulse generator based on FPGA technology. This part introduces a second pulse generator device based on FPGA technology, and then describes the hardware design of the second pulse generator device.